About Commit Protocols and Journaling

The safe, remote, and region commit protocols coordinate messages to the journal with transaction commits. If an SM process terminates unexpectedly, journaling messages are used to ensure that the archive is in a consistent state when it rejoins the database.

Replication files that are required for journaling are stored in a specified journal directory; if not specified, the default directory is journal in the archive directory.

Caution: For performance and latency purposes, it is best to have the journal and the archive on different disks. A further improvement would entail using different disk controllers. However, if neither the journal nor the archive is available, (or one of them is corrupt), an SM will not start.

For data durability:journaling is always enabled.

For redundancy purposes:at least two SMs should be used.

See the Database Options page for details about these and other database options.

Note: You can configure these options with the NuoDB Manager, the REST API Reference, or in the nuodb.config file.